Abstract Although the majority of existing combustion devices operate at high pressure conditions, most of our understanding of the soot formation process and soot physicochemical properties rely on studies performed at atmospheric pressure. Pressure is known to have nonlinear effects on combustion processes and a significant influence on soot formation; soot loading increases with increasing combustion pressure. Soot characteristics directly affect soot oxidation and optical/radiative properties, and it is desirable to have a better insight into them under high-pressure conditions. Due to scarcity of information on soot primary particles, aggregate morphology, and soot nanostructure relevant to high-pressure combustion, there are challenges in predicting soot oxidation and radiation, particularly at engine-relevant conditions. In this study, we perform Raman spectroscopy measurements on soot sampled from a set of laminar diffusion flames of ethylene at various pressures, ranging from atmospheric pressure to 12 bar. Our results show an increase in soot maturity as the pressure increases within the range of investigated pressures. In the examined co-flow flames, pressure seems to have an indirect influence on soot nanostructure through an earlier inception of soot, resulting in longer residence times of the carbon soot particles in the hot and reactive flame environment. It is found that soot maturity, tracked through the size of graphitic domains, La, increases linearly with residence times. The longer residence time of soot in high-pressure flames could be the main cause of the higher degree of graphitization observed, which suggests a greater resistance to oxidation with increasing pressure.

中文翻译：

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压力对碳烟纳米结构的影响：拉曼光谱研究

摘要 尽管大多数现有的燃烧装置都在高压条件下运行，但我们对烟尘形成过程和烟尘物理化学性质的大部分理解依赖于在大气压下进行的研究。众所周知，压力对燃烧过程具有非线性影响，并对烟灰形成有显着影响；烟尘负荷随着燃烧压力的增加而增加。烟尘特性直接影响烟尘氧化和光学/辐射特性，希望在高压条件下更好地了解它们。由于与高压燃烧相关的烟尘初级粒子、聚集体形态和烟尘纳米结构的信息稀缺，因此在预测烟尘氧化和辐射方面存在挑战，尤其是在发动机相关条件下。在这项研究中，我们对从大气压到 12 巴的各种压力下从一组乙烯层流扩散火焰中取样的烟灰进行拉曼光谱测量。我们的结果表明，随着压力在研究压力范围内增加，烟灰成熟度增加。在检查的共流火焰中，压力似乎通过较早的烟灰开始对烟灰纳米结构产生间接影响，导致碳烟灰颗粒在热和反应性火焰环境中的停留时间更长。发现通过石墨域 La 的大小跟踪的烟灰成熟度随停留时间线性增加。烟灰在高压火焰中的较长停留时间可能是观察到的石墨化程度较高的主要原因，